Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations only declare readOnlyHint=true; the description adds real behavioral context beyond that: an API key requirement (auth prerequisite) and a live-check latency warning with an explicit anti-pattern. That is meaningful disclosure for a tool whose annotations cover only the safety profile.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences with zero filler, and the most important operational warning (latency, no looping) is front-loaded alongside the resource definition.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a one-parameter read tool with no output schema, the description covers what data is returned, the auth requirement, and the latency caveat. It leaves the response shape unspecified, but that gap is minor given the tool's simplicity.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% for the single postcode parameter, so the schema already carries the semantics. The description adds no format guidance (e.g. spacing/case of UK postcodes) beyond what the schema states, making 3 the correct baseline.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific resource (Ofcom broadband and mobile coverage) scoped to a postcode, which clearly distinguishes it from sibling data tools like get_flood_risk or get_epc_history. It does not explicitly name a sibling, so it lands just short of a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides a concrete usage constraint — 'do not call it in a tight loop over many postcodes' — which tells the agent when not to use it in bulk. It does not, however, say when this tool is preferred over or combined with siblings such as get_property_summary.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.